1. Field of the Invention
The present invention relates to a liquid supply device capable of stirring liquid stored in a liquid tank.
2. Description of the Related Art
In recent years, in an ink jet recording apparatus as one type of liquid ejection apparatus, pigment ink excellent in weather resistance has been mainly used. However, when the pigment ink is left unused in an ink tank for a long period of time, pigment settles on a bottom portion of the ink tank. Therefore, concentration and viscosity of the pigment ink become nonuniform due to fluctuation thereof depending on the position inside the ink tank. When the pigment ink in this state is supplied to an ink jet recording head in order to perform recording, the following problems occur. A jetting characteristic of the ink may fluctuate for each recording. Further, due to the ink having high concentration and high viscosity, a narrow portion of the ink jet recording head, such as an ink flow path portion, a filter portion, and a nozzle, may be clogged, and in the worst case, ejection failure may occur. Still further, due to the nonuniformity of the concentration of the ink, recording quality may become nonuniform. Therefore, it is essential to keep uniform concentration and viscosity of the ink in the ink tank. To keep uniform concentration of the ink before use, it is necessary to take measures such as shaking the tank and stirring the ink in the tank. Further, a period of time to elapse until the concentration and the viscosity of the pigment ink fluctuate and become nonuniform differs depending on colors, and hence it is important to stir the ink.
In view of this, in Japanese Patent Application Laid-Open No. 2010-143050, the ink in the ink tank, which is configured to store the ink, is stirred in such a manner that the ink is caused to flow backward into the ink tank from a sub tank, which is configured to temporarily store the ink supplied from the ink tank and transport the ink to a recording head. Specifically, a bellows is provided so as to communicate to the sub tank, and a valve is provided on a flow path connecting the ink tank and the sub tank to each other. The sub tank is pressurized by the bellows under a state in which the valve is closed. After that, the valve is opened, and the ink in the sub tank flows backward into the ink tank due to a pressure difference therebetween. In this manner, the ink in the ink tank is stirred.
Further, in Japanese Patent Application Laid-Open No. 2010-214721, two flow paths each connecting the ink tank and the sub tank to each other are provided. The ink is circulated through the two flow paths. In this manner, the ink in the ink tank is stirred.
However, in the case of the method disclosed in Japanese Patent Application Laid-Open No. 2010-143050, only an amount of the ink, which corresponds to a deformation volume of the bellows, flows backward into the ink tank, and hence the amount of the ink that flows into the ink tank is small. Therefore, the amount of the ink that flows into the ink tank cannot be increased unless the ink is repeatedly caused to flow backward from the sub tank into the ink tank. Thus, a longer period of time is required for a stirring operation for the ink. Further, when dealing with the above-mentioned problem by providing a larger bellows, the bellows is required to have a volume equivalent to that of the ink tank. Thus, the device is upsized.
Further, in the case of Japanese Patent Application Laid-Open No. 2010-214721, liquid cannot be caused to forcefully flow from the sub tank into the ink tank, and hence a longer period of time is required to stir the ink.